FPGA-Based Smart Sensor for Online Displacement Measurements Using a Heterodyne Interferometer

Luis Alberto Vera-Salas,Arturo Garcia-Perez,Eduardo Cabal-Yepez,Sandra Veronica Moreno-Tapia,Rene De Jesus Romero-Troncoso,Roque Alfredo Osornio-Rios,Ibrahim Serroukh

doi:10.3390/s110807710

Abstract

The measurement of small displacements on the nanometric scale demands metrological systems of high accuracy and precision. In this context, interferometer-based displacement measurements have become the main tools used for traceable dimensional metrology. The different industrial applications in which small displacement measurements are employed requires the use of online measurements, high speed processes, open architecture control systems, as well as good adaptability to specific process conditions. The main contribution of this work is the development of a smart sensor for large displacement measurement based on phase measurement which achieves high accuracy and resolution, designed to be used with a commercial heterodyne interferometer. The system is based on a low-cost Field Programmable Gate Array (FPGA) allowing the integration of several functions in a single portable device. This system is optimal for high speed applications where online measurement is needed and the reconfigurability feature allows the addition of different modules for error compensation, as might be required by a specific application.

Highlights

In the recent evolution of different industrial processes, the measurement of small nanometric scale displacements demands metrological systems of high accuracy and precision, even in the toughest environments
The novelty of this work is the fusion of these techniques and the implementation in an Field Programmable Gate Array (FPGA) allowing the system to achieve high speed measurements, on the order of MHz, the system is optimal for high speed and for a wide range of measurement applications, while the reconfigurability feature allows the addition of different modules for error compensation as required by each application
In this experiment the precision of the smart sensor is evaluated by using a stage micrometer

Summary

Introduction

In the recent evolution of different industrial processes, the measurement of small nanometric scale displacements demands metrological systems of high accuracy and precision, even in the toughest environments. Interferometry-based displacement measurements, those using the dual-frequency laser feedback effect interferometer considered in [1], have become the main instrument employed for traceable dimensional metrology. Displacement measurement systems based on this technique usually achieve a resolution of 79.1 nm. Higher resolution is required in the most recent high-precision measurement applications. In this context increasing the resolution of nanometric measurements remains an open problem [2]. On the other hand an acceptable measurement speed is desirable in modern applications [3,4] and the use of high-speed electronic systems can solve this necessity

Methods

Results

Conclusion